Voltage standards for residential and industrial lighting vary in magnitude and frequency from one country to the next. Most of the industrialized nations of the world employ AC power for lighting. The most common frequencies vary from 50 Hz in many European countries and China to 60 Hz in North America and Taiwan. Aviation electrical supplies are most commonly 400 Hz.
While the variation of AC line frequency is fairly tight among different countries (50-60 Hz) the variation in line voltage is considerably greater; ranging from 110V in the US to 240V in various European countries and China. Different standards include 100V, 110V, 120V, 208V, 220V and 240V. At this point in time there is no international standard nor is it likely that there will be in the near future because of the huge infrastructure investments in existing electrical power grids in different countries. There is no one “right” answer as to what is the proper voltage. In fact, many people now believe that the decision to use AC power instead of DC power as the norm has turned out to be a less than an ideal decision.
Besides voltage variations between countries there can also be substantial variations within one country and even within one building. In the US one can find 110V, 117V, 120V, up to 277V or even higher, all in one building. For instance, in a US company the office area may be wired with 120V, while the factory area might be wired for 208V. This situation is much more common than one may think at first.
Light emitting devices, more commonly known as light bulbs, whether they are fluorescent, incandescent, white light emitting diode (WLED), cold cathode fluorescent (CCFL), or other types must, by their nature, be designed to run over a voltage range that is much tighter than that found around different countries or even within a single building. If a bulb of any type, designed to run at 110V, was mistakenly used in a fixture wired for 220V the result would be almost certain failure, probably catastrophic and even potentially dangerous. If the lamp did not fail immediately then a slow failure might be even more dangerous since it might not be immediately detected. Instead of immediate failure it could overheat slowly causing a serious fire hazard at a time when no one may be around to notice it and take appropriate action. Safety is arguably the biggest problem associated with improperly matching a lamp to its input line voltage.
A large number of different types of lamps are required to satisfy the lighting needs of so many different supply voltages. The logistics of manufacturing so many different light emitting devices, as well as the complications of transporting and warehousing those light emitting devices increases the costs of those light emitting devices. It may also increase the energy required to produce those devices as well as increase the green house gas emissions (and other unwanted byproducts) that result from the manufacture of those devices.
What is needed is a light emitting device that is tolerant of a wide range of power supply voltages.
Keeping the drawbacks of the prior art in mind, and employing experiments and research persistently, the applicants finally conceived a universal input voltage light emitting device.